CUSPIDATES. 



213 



small circular discoidal spot, and again be- 

 yond this are certain zigzag blackish lines, 

 the outer of which expands into a large 

 transverse dark gray blotch on the costa ; 

 on the margin itself is a series of eight 

 small circular black spots : the hind wings 

 of the male are white, with an occasional 

 smoke-coloured cloud and a marginal series 

 of black dots ; in both sexes, but particu- 

 larly the female, they have occasionally a 

 broadish smoke - coloured hind - marginal 

 band, terminating in a diffuse spot at the 

 anal angle. The head and collar are white ; 

 the thorax whitish, varied with smoky- 

 black; the body gray, with smoke-coloured 

 bands. 



The Baas are laid separately on the 

 upper surface of the leaves of aspen (Popu- 

 lus tremula), the female selecting those 

 dwarf shrubby plants which grow in 

 woods ; and in gardens on the leaves of 

 tacamahac (Populus fcaZsami/'era), about the 

 1st of July, and the young CATERPILLAR 

 emerges about the 14th ; it appears to be 

 full-grown about the 26th. It spins a silky 

 coating near the middle of the leaf of its 

 food-plant, and, attaching itself to this, 

 both by its feet and claspers, it is very 

 difficult to remove ; it remains perfectly 

 without motion during the day, exposed to 

 the rays of the sun, and feeds during the 

 night. After feeding it sometimes remains 

 clasping the margin of the leaf it has been 

 eating; when at rest the head is nearly 

 withdrawn into the second segment. The 

 eleventh, twelfth, and thirteenth segments 

 are elevated, and the anal horns are closely 

 approximate and pointing in a straight line 

 backwards ; the head is prone, and narrower 

 than the second segment into which it is 

 received ; the body rises from the head to 

 the fourth segment, which is produced into 

 a transverse dorsal ridge, whence the body 

 gradually tapers to the anal extremity, the 

 eleventh, twelfth, and thirteenth segments 

 forming a cone ; at the anal extremity are 

 two cylindrical tubes, each of which is 

 covered with short bristles, which give it a 

 scabrous feel as well as appearance ; and 

 each of which also contains a slender fila- 

 ment capable of being protruded at the will 

 of the caterpillar. The colour of the head 



is grayish-brown, the sides dark brown, the 

 face delicately reticulated ; the dorsal area 

 of the body is gray-brown, marbled with 

 darker and lighter shades, and bordered 

 throughout with bright yellow ; the lateral 

 and ventral areas are bright apple-green, 

 dotted with purple-brown, and every dot 

 emitting a small black bristle. On the 

 fifth segment the green colour extends 

 completely round the caterpillar, interrupt- 

 ing the dorsal brown area, which recom- 

 mences in a point and increases in breadth 

 to the eighth segment, on which it descends 

 below the spiracle ; it then gradually nar- 

 rows to the twelfth segment, and again 

 expands on the thirteenth. The anal tubes 

 are green, with a brown patch on the inner 

 side of each near the base ; they have a 

 brown ring beyond the middle, and a 

 second paler ring at the tip ; the filaments 

 are black, the spiracles brown ; the ventral 

 surface of the segments is blotched with 

 brown ; the legs are green, each joint hav- 

 ing a red mark on the outside. When full- 

 fed this caterpillar excavates a portion of 

 the bark of the tree on which it feeds, and 

 in this constructs a very strong glutinous 

 cocoon, so like the bark in colour as to be 

 seen with difficulty. 



The MOTH appears on the wing in June, 

 and is very widely distributed in England ; 

 and Mr. Birchail says it is not uncommon, 

 and is widely distributed in Ireland. (The 

 scientific name is Dicranura bifida, and this 

 name also includes Cerura arcuata and C. 

 fuscinula of Stephens.) 



Obs. Notwithstanding the perfect con- 

 viction I feel that Dicranura furcula and 

 D. bifida are distinct species, I am bound 

 to acknowledge my inability to make the 

 difference apparent in words. The exterior 

 margin of the median band in D. furcula 

 is generally more concave or scooped out 

 below the costa than in D. bifida; the 

 median band is darker coloured in bifida, 

 it is more inclined to orange in furcula ; 

 bifida is also a larger insect ; but these are 

 comparative differences only, and therefore 

 we must appeal to the differences in food 

 and colour of the caterpillars, when all 

 doubt of the distinctness of the species will 

 be at once removed. 



